The present invention concerns copolymers of vinyl chloride and the process of making said copolymers.
It is know to prepare polymers of vinyl chloride of high molecular weight by polymerization at temperatures below 40.degree. C. However, polymerization at such a low temperature involves difficulties of thermal regulation, necessitating the use of a cooling apparatus.
As discussed herein, the molecular weight of a polymer of vinyl chloride is obtained from its viscosity index determined according to international standard ISO 174.
It has been proposed to prepare copolymers of vinyl chloride of high molecular weight by the polymerization of vinyl chloride at a temperature equal to or above 40.degree. C. in the presence of a polyfunctional compound. As used herein, the term "polyfunctional compound" means a compound whose molecule includes at least two ethylene double bonds. Numerous polyfunctional compounds have been utilized such as, for instance, diallyl phthalate, diallyl oxalate, diallyl sulfide, diallyl ether, diallyl maleate, triallyl phosphate, divinyl ether, polyalkylene glycol dimethacrylate, polyether glycol dimethacrylate, and polyester glyco dimethacrylate. However, the copolymers obtained have a weight percentage of insoluble matter in tetrahydrofuran which is generally above 10% and can reach 80%, rending their use difficult. At a polymerization temperature equal to or above 40.degree. C., with the help of polyfunctional compounds used up to the present time, it is especially not possible to obtain copolymers of vinyl chloride exhibiting at the same time a viscosity index above 250 ml/g and a weight percentage of matter insoluble in tetrahydrofuran below 5%.